1. Field of the Invention
The present invention relates to a building board printing apparatus, and in particular to a building board printing apparatus, which uses ink jet printing technology without plate-making, and which is adapted for a small-lots and multi-products manufactured system.
2. Description of the Related Arts
In the field of industrial multi-color printing machines, a gravure printing machine has been currently in use. The gravure printing machine has four separated gravure printing rollers for multi-color printing, which colors are C-color (cyan), M-color (magenta), Y-color (yellow), and B-color (black). Each color printing is carried out sequentially. Namely, in gravure printing, multicolor printing is accomplished by using four printing rollers as plates.
In the field of office machines, ink jet printers have been developed to a high degree in Japan. By using ink jet printers, simultaneous full-color printing with extremely high image resolution has been realized without implementing any plates for printing. Ink jet printers have one printing head for jetting color-inks (C, M, Y, B) simultaneously. The printing head has many jetting nozzles which control the open and shut movements by piezo-vibrator elements having high responsibility for voltage.
Nevertheless, although ink jet printers are aimed at desk-top level printing, one defect is that they have slow printing speeds (e.g. it is presently the case that color printing of an A4 page takes 1 to 5 minutes).
Therefore, even though ink jet printers have a huge advantage in that they can realize good-quality simultaneous full-color printing with high resolution, when considering the application thereof to the building board color printing field, there are considerable difficulties involved in the direct introduction of these printers in their present form into this field.
Considering the industrial printing of building boards, in order to cope with high manufactured-line speed (e.g. 24 m/min.) and to cope with building boards having extremely large printing faces, which are incomparable with paper, it is necessary to arrange a large number of jetting nozzles in a direction orthogonal to the moving direction over a range sufficient to cover the width of building boards.
A method for color printing of building boards, which applies piezo-vibration technology and a drop ink jetted from each jetting nozzle, is disclosed in Japanese Publication of Unexamined Patent Application (kokai) Nos. 9-201564 and 10-128231.
Nevertheless, the disclosed printing head, having a large number of nozzles arranged thereon, jets only one color ink from each nozzle. Thus, it is necessary to separately install the plurality of printing heads corresponding to the number of colors in multi-color printing, and ink jet printing is carried out sequentially.
Japanese Publication of Unexamined Patent Application (kokai) 3-13347 discloses a full-color industrial printing method using a thermal jet technology. However, in this method, a recorded printing of a page width of 216 mm is performed at 16 dots/mm nozzle pitch. Thus, this device configuration is unsatisfactory for building board full-color industrial printing. That is to say, this method involves difficulties in fabrication with respect to the precision of nozzle pitch in a case where printing heads are extended to a broad object to be printed, and thereby results in high fabrication cost. Moreover, even where a printing head can be produced with high precision, the problem of long-term operation still remains. This could cause substantial impairment of productivity, since there is a need to remove the entire printing head for exchange or repair when pigmentation of a portion of a printing head, or malfunction of the electronic system occurs.
In contrast, Japanese Publication of Unexamined Patent Application (kokai) 4-99688 discloses a method involving industrial printing of a sheet-shaped object, in which a nozzle arrangement at a given pitch is realized with good precision by arranging a large number of small-scale printing heads having a given number of nozzles. However, in this method also, one printing head jetting one color of ink was divided into multiple small-scale printing heads so as to make a group printing head configuration. A number of group printing heads corresponding to the number of colors in multi-color printing use is also required herein.
Thus, with any one of the above-stated methods, problems remain with respect to the realization of a stable simultaneous full-color industrial printing.
As disclosed in Japanese Publication of Unexamined Patent Application (kokai) 9-11509 for example, regarding a printing head in office work equipment, four nozzle arrays, which comprise the given number of nozzles jetting inks of four colors such as cyan, magenta, yellow and black, are equipped on a particular printing head. With ink jet printers in office work equipment, the particular printing head simultaneously jets the color inks of the above four colors on a page. The printing head traverses the page without contacting the page to be printed.
Furthermore, as disclosed in Japanese Publication of Unexamined Patent Application (kokai) 9-1832, there also exists a printing head having each nozzle array arranged in parallel thereon, which jets each ink such as cyan, magenta, yellow and black.
However, all of these printing head configurations are only directed to a desk-top level paper printing and relate to a technology involving allowing a printing head to traverse across the face to be printed. Thus, there is no way to apply these technology to building board full-color industrial printing.
Where printing is performed while ink jet nozzles are arranged in a direction (a main scanning direction) orthogonal to the direction to which the building boards are moved, there is conventionally adopted a configuration that nozzle arrays jetting the same color are arranged in a main scanning direction. The nozzle arrays jetting the different colors are successively arranged in a vice scanning direction providing relatively large intervals. For this reason, where a full-color printing is performed using, e.g., inks of four colors, C, M, Y and B, building boards must be moved for a long distance, while the given pixel of the building board passes all of the nozzle positions jetting the four colors.
Hence, when the distance between nozzles jetting each color in the vice scanning direction is long, building boards may be displaced in the main scanning direction while the building boards are carried for the distance between nozzles, or the amount of deviation of printing position may be increased by mere fluctuation of building board moving velocity, thus resulting in reduction in the quality of printed image or pattern. On the other hand, to reduce the amount of deviation of printing position within a given range, a higher carrier precision of building boards is required in proportion to a distance between nozzles containing each color of ink.
Therefore, the present invention is directed to solve the above-stated problems, and an object of the present invention is to provide a building board printing apparatus capable of shortening the printing interval between different colors in a vice scanning direction to achieve a high-quality printing with low color deviation.
To accomplish the above object, the building board printing apparatus of the present invention comprises a plurality of printing heads having a plurality of colors of ink jet nozzle arrays arranged in a main scanning direction on a per color basis, wherein the printing heads are arranged in a vice scanning direction while being shifted in a main scanning direction on a color unit basis.
Moreover, the feature that the nozzle arrays are arranged in a line in a main scanning direction enables the entire building board to be printed using few nozzles.
Furthermore, the feature that the shift occurs color by color enables the printing heads to be orderly arranged in a diagonal direction, resulting in easy fabrication.
Still further, the feature that the plurality of colors consist of 4 colors enables high printing quality.
The specification includes part or all of the contents disclosed in the specification and/or drawings of Japanese Patent Application No.2001-048834, which is a priority application of the present application.